1. Field
The following description relates to an envelope tracking power amplifying apparatus and method.
2. Description of Related Art
A significant concern in the design of recent digital communications systems is improving power efficiency. In methods for improving the efficiency of power amplifiers in broadband mobile communications systems, a method of using an envelope tracking power amplifier (ETPA), which is a type of high-efficiency power amplifier, has attracted interest.
In general, high efficiency power amplifiers have non-linear characteristics. Thus, as a method for reducing nonlinearity, a digital predistortion (DPD) method is commonly used. In such a method, input signals are compensated for by being inverted with respect to nonlinear characteristics of signals in digital regions.
However, as envelope signals have bandwidths that are three or four times wider than those of baseband signals, limitations exist to improve performance through a digital predistortion method and, accordingly, negatively affects power efficiency.
To this end, the use of methods in which envelope signals are passed through low pass filters has been known, but by using such an approach, memory effects in which interference occurs between adjacent samples to which outputs from envelope tracking power amplifiers are transferred may occur.